The VVT controller is disposed in a torque transfer system which transfers the torque of the driving shaft of the engine to the driven shaft which opens and closes at least one of an intake valve or an exhaust valve. The VVT controller adjusts the valve timing of the valves by varying a rotational phase of the driven shaft to the driving shaft.
JP-2002-227616A shows a VVT controller having a sprocket which rotates in synchronism with the driving shaft, and a rotational phase adjusting mechanism which connects levers with the driven shaft via link arms. The phase adjusting mechanism converts a movement of the link arms into a relative rotational movement of the levers to the sprocket and varies the rotational phase of the driven shaft relative to the drive shaft.
In this conventional controller, guide balls held by the operation member are slidably engaged with a groove of the sprocket. When an engine torque is varied and some force are applied to the phase adjusting mechanism, the operation member may slide in the groove so that the rotational phase of the driven shaft unnecessarily varies relative to the driving shaft.